1. Leakage at the hydraulic hose

The leakage of hydraulic hose includes the leakage caused by the long-term wear of the rubber hose part and the leakage at the hose joint. The leakage of the hose joint mainly occurs near the joint surface of the hose joint and the hose buckle, and the assembly seal of the hose joint and the straight joint. The main causes of rubber hose leakage are: unqualified size of the hose joint; inadequate crimping of the hose; loosening of the joint due to hydraulic shock or mechanical vibration; unreasonable direction of the hose; inappropriate tightening torque for the hose assembly; Qualified; the pressure level of the hose is not properly selected.

2. Surface leakage of hydraulic parts

The surface leakage of hydraulic parts mostly occurs on the casting surface and welding parts, which is caused by the gradual expansion of component design defects and production defects under the pressure pulsation or shock vibration of the hydraulic system.

(1) The main causes of casting surface leakage are: casting defects such as shrinkage cavities and porosity in parts; unreasonable design of casting wall thickness; unreasonable selection of casting materials; processing errors.

(2) The reasons for the leakage of the welding part mainly include: unreasonable design of the welding method; incomplete filling of the welding groove; defects such as pores in the weld; insufficient fixation of long welded pipe fittings, etc.

3. Leakage at the bonding surface of hydraulic components

The joint surface of components in the hydraulic system of construction machinery mainly includes: the connection surface of each component oil port and hydraulic joint, the hydraulic confluence block, the connection surface of welded steel pipe and hose, the sealing surface between the main valve plates, and the installation surface between components, etc. The leakage of these joint surfaces is mainly related to design, processing and assembly: unreasonable design of sealing groove size; excessive error of sealing surface roughness and flatness, poor processing quality; improper selection of sealing structure, resulting in deformation, so that the joint surface cannot be comprehensive contact; improper assembly; scratches on the sealing surface.

4. Seal leakage

The leakage of the seal is caused by the damage of the seal or the reduction of the sealing effect, which is mainly manifested in the following aspects: the material of the seal does not match the service conditions; the compression of the seal is not enough; the aging of the seal is caused by improper storage; Indicators such as the pressure level do not meet the requirements; the assembly method of the seal is unreasonable; impurities cause wear and damage to the seal; excessive oil temperature leads to accelerated aging of the seal. Due to the mixing of impurities, the sealing ring of the end cover is worn out by impurities during the continuous rotation of the steering gear, which eventually leads to external leakage of hydraulic oil under high pressure.

5. Leakage between valve core and valve body

The hydraulic system of construction machinery includes various control components such as working valves, pilot valves, and integrated valve groups. Cartridge valves are usually installed on the components, such as relief valves, check valves and solenoid valves. In order to achieve good control characteristics, such components The matching gap between the valve core and the valve body is very small, so higher requirements are put forward for the design, production and maintenance of the product. The reasons for the leakage between the valve core and the valve body include: the cleanliness of the hydraulic oil is not up to the standard; the gap between the valve core and the valve body is out of tolerance; the spring is invalid; The unreasonable design of the pressure groove leads to uneven force on the spool

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